This invention relates to approaches for drying chemical compositions deposited on substrate in solution form. The invention is particularly suited for drying solution to produce reagent test strips for use in analyte determination assays, especially for electrochemical determination of blood analytes.
Analyte detection assays find use in a variety of applications including clinical laboratory testing, home testing, etc., where the results of such testing play a prominent role in the diagnosis and management of a variety of conditions. The more common analytes include glucose, alcohol, formaldehyde, L-glutamic acid, glycerol, galactose, glycated proteins, creatinine, ketone body, ascorbic acid, lactic acid, leucine, malic acid, pyruvic acid, uric acid and steroids, etc. Analyte detection is often performed in connection with physiological fluids such as tears, saliva, whole blood and blood-derived products. In response to the growing importance of analyte detection, a variety of analyte detection protocols and devices for both clinical and home use have been developed. Many detection protocols employ a reagent test strip to detect analyte in a sample.
As the demand for reagent test strips has grown, the need for evermore efficient and flexible manufacturing approaches has increased. Still, little improvement has been made with respect to the handling of reagent material incorporated into test strips.
In producing reagent test strips, a coating of biological reagent which usually includes heat labile or moisture sensitive biological components (after drying for shelf stability) in a low viscosity aqueous solution is typically applied to a substrate used to produce one or more strips. Many existing systems designed to dry such biological reagents use high-velocity air impingement techniques to dry coating applied in aqueous form to a substrate. While effective to a certain extent, there are disadvantages associated with these currently employed techniques, typically due to low heat that may be applied and high air impingement rates necessary for drying in a reasonable amount of time.
As such, there is great interest in the development of new techniques for drying a liquid reagent composition with low viscosity and surface tension that has been applied to a substrate. The present invention satisfies this need by providing an improved approach to drying a liquid coating or composition applied to a substrate. Specifically, the present invention avoids problems commonly associated with high-velocity air impingement drying such as poor efficiency, slow desiccation, solution disturbance due to airflow. Various features of the invention offer increased manufacturing efficiency, a concomitant reduction in manufacturing cost and/or improved test strip quality. Further possible advantages of the present invention may also be apparent to those with skill in the art.
The present invention includes devices and methods for drying solution, typically having a viscosity less than 100 centipoises (cP), most often around 1.5 cP, that is applied to the surface of a material or substrate, especially for use in producing reagent test strips. Finished product made using the systems disclosed also form part of the invention. Typically, the product will be in the form of complete reagent test strips. Alternately, test strip precursors including at least substrate material with chemical solution dried thereon may be regarded as the product of the present invention.
The invention employs radiant energy to dry solution applied to a substrate. A non-disturbing airflow may be provided to enhance drying speed. Substrate with a chemical coating dried thereon according to the present invention may be used in a variety of types of test strips. Preferably, substrate processed according to the present invention preferably includes a metallic surface. Such a coating dramatically increases the potential for energy application. Furthermore, a metallic or metal-coated substrate is easily incorporated in electrochemical-type test strips.